The Meraglim Lacked Emunah:
In Parshas Devarim, the Torah informs us that the root of the sin of the meraglim was their lack of emunah, as is stated (Devarim 1:32): ‘In this matter, you did not believe in Hashem.’ The Ramban writes that with these words, Moshe Rabenu was chastising the people for the sin of the meraglim. He told them, ‘You were right that the residents of the land are strong and mighty. But Hashem will fight for you, just like he did in Egypt. In this matter, you did not believe in Hashem. It was all a result of a lack of emunah.’
Thus, the lesson we are meant to learn from the story of the meraglim is to strengthen our emunah. In our times, when we are facing troubles on all sides, we can only merit salvation through emunah.